Unexamined Japanese Patent Publication No. 2006-301195 discloses one type of a hybrid drive apparatus for hybrid vehicles. In this hybrid drive apparatus, a target drive torque for a vehicle wheel drive system, a target motor-generator torque and a target engine torque are calculated based on an accelerator pedal depression amount, vehicle speed, state of charge of a battery and engine speed.
As taught therein, a target drive torque is calculated based on an accelerator pedal depression amount and a vehicle speed. Then, an engine torque that optimizes the fuel consumption efficiency of the engine is retrieved based on an engine rotation speed by reference to a fuel consumption efficiency optimizing control map. A retrieved fuel consumption efficiency optimizing engine torque is determined as a target engine torque. Then, a target motor-generator torque is determined so that the sum of the target engine torque and the target motor-generator torque is equal to the target drive torque.